P. V. Ramesh Babu

Genetic implications of rare uraninite and pyrite in quartz-pebble conglomerates from Sundargarh district of Orissa, Eastern India

Petrographic and EPMA studies reveal the presence of discrete grains of uraninite and pyrite are being reported for the first time in quartz-pebble conglomerates from western margin of Bonai granite pluton, Sundargarh district, Orissa. Uraninite grains (2–3 μ in size) are subrounded to muffin shaped which show variation in UO2 (63.86 to 71.73 wt %), ThO2 (5.48 to 6.42 wt %) and RE2O3 (1.57 to 2.23 wt %). Pegmatitic source of uraninite is revealed by comparing UO2, ThO2, PbO, CaO content and ratios of UO2/ThO2 and CaO/ThO2 in uraninites from pegmatite and other environments and areas. Subrounded to muffin shape of uraninite, their association with subrounded pyrite and heavies like zircon, tourmaline, chromite, monazite, magnetite and their comparable chemistry with well established quartzpebble conglomerates of India and world are indicative of their detrital origin. Pyrite, minor chalcopyrite and rare galena are observed as sulphide phases in conglomerate. Variable shapes of pyrite, their low Co (up to 0.16 wt %) and Ni contents (up to 0.09 wt %) and Co/Ni ratio less than 1.0 (mean= 0.63) favours sedimentary/diagenetic origin.

Bastnaesite from Kanigiri granite, Prakasam district, Andhra Pradesh

For the first time we report bastnaesite and hydroxyl bastnaesite (lanthanum cerium fluoro-carbonate) from the Kanigiri granite. The host granitoids are of A-type and vary in composition from quartz syenites to peralkaline granites. Rare metal and rare earth-bearing minerals identified by X-ray diffraction (XRD) studies in Kanigiri granite are bastnaesite and hydroxyl bastnaesite, besides columbite-tantalite, monazite, fergusonite, thorite and euxenite. Petromineralogical studies have also revealed the presence of bastnaesite. The presence of bastnaesite in Kanigiri granite suggests that the host felsic rocks may also form a potential source for light rare earth mineral, bastnaesite, apart from the already known rare-metal minerals.

A new occurrence of thorianite from syenitic pegmatite near Bhaluchuan, Odisha

We report a new occurrence of thorianite from syenitic pegmatite near Bhaluchuan, Sambalpur district, Odisha. The thorianite is brown to deep-brown with round grains of 2 to 10 mm size. The chemical analysis of the investigated thorianite reveals 64.8% ThO2, 25% U3O8, 3.81% PbO and 1.7% Fe2O3. Calculated structural formula of the thorianite is (Th+40.61U+40.14U+60.08ΣREE+30.017Pb+20.04Ca+20.01Mn+20.001Fe+30.05Al+30.003Sc+20.002K+10.005Na+10.008 Si+40.04Ti+40.02)O2.08. Chondrite-normalised rare-earth element (REE) plot of the thorianite reveals enrichment of light REE (LREE) over heavy REE (HREE) with pronounced negative Eu-anomaly (Eu/Eu* = 0.35). The (ΣLREE/ΣHREE)N ratio is perceptibly high (2.76). The (La/Lu)N (42.31), (La/Yb)N (27.49) and (Ce/Yb)N (21.58) ratios are also very high.X-ray diffraction (XRD) pattern of the investigated thorianite displays sharply-defined reflections. Corresponding interplanar spacings (d-spacings) of all the reflections are in very close agreement with those published for thorianite standard in International Centre for Diffraction Data (ICDD) Card No. 4-556. However, I/Io of two reflections (1.9694Å and 1.6787Å) are lower than those published for thorianite standard. The unit cell parameter (ao) of the investigated thorianite (ao 5.5750Å) is also less than ao of thorianite standard (ao 5.6000Å and V 175.62Å3), which is because of extensive substitution of Th by U.

Ianthinite: A rare hydrous uranium oxide mineral from Akkavaram, Andhra Pradesh, India

Ianthinite is the only known uranyl oxide hydrate mineral that contains both U6 +  and U4 + . For the first time, we report ianthinite from India (at Akkavaram, Andhra Pradesh), which is hosted in basement granitoids. The mineral occurs in the form of tiny grains, encrustations and coatings in intimate association with uraninite and uranophane. X-ray diffraction (XRD) data reveals that d-spacings of the investigated ianthinite are in close agreement with the corresponding values given for ianthinite standard in International Centre for Diffraction Data (ICDD) card no. 12-272. The crystallographic parameters of the studied ianthinite are: ao = 11.3 (1) Å, bo = 7.19 (3) Å and co = 30.46 (8) Å, with a unit cell volume of 2474 (27) Å3. The association of investigated ianthinite with uraninite suggests that the former has formed due to oxidation of the latter. Since a major part of the uraninite was exposed to oxidizing meteoric water, much of it has been transformed into hydrous uranium oxide (ianthinite) and very little part remained unaltered as uranium oxide (uraninite). Absence of schoepite in the investigated ianthinite suggests that after its formation it (ianthinite) was not exposed to oxygen/oxidizing meteoric water. As the oxidation was partial and short lived, some amount of primary uraninite is also preserved.

Signature of potassium enrichment in granite of the Chitrial area, Nalgonda district, Andhra Pradesh: Inferences using its U, Th, K2O, Na2O, Rb, Ba and Sr contents

A medium tonnage unconformity proximal uranium deposit has been established at Chitrial by the Atomic Minerals Directorate in the Srisailam sub-basin. In this type of deposits, the association of uranium with potassic alteration (illitization) is well-documented. The present study is directed towards understanding such an association in the Chitrial area for which the uranium mineralized borehole core samples were collected and analyzed. It is observed that the average concentrations of K2O, Na2O, Rb, Ba and Sr in the granite of the Chitrial area are 5.35%, 1.78%, 252 ppm, 564 ppm and 52 ppm, respectively, and they show average critical elemental ratios of K/Rb, Ba/Rb and Rb/Sr as 191, 2.37 and 7.13, respectively. The granites show low K/Rb, low Rb/Ba and high Rb/Sr ratios compared to that of the average crust indicating its derivation from crustal source. The samples have higher values of uranium (av. 53 ppm), thorium (av. 66 ppm) and lead (av. 41 ppm). The U/Th ratio in the granite varies from 0.07 to 20.86 with an average of 1.68. They also exhibit high K2O/Na2O ratio typical of post-Archaean granite and very high values suggest the possibility of later potassium enrichment.

Mineral chemistry of tourmaline from Mashak Pahar, South Purulia Shear Zone (SPSZ), eastern Indian Shield

The area of investigation at and around Mashak Pahar, Bankura district, West Bengal, India comprises a number of rock types namely: granite gneiss, migmatized quartz tourmaline gneiss, quartz pebble conglomerate, ferruginous quartzite, quartz tourmaline veins (as veins) and graphite schists. Interestingly, the study area lies in the region extending South Purulia Shear Zone (∼Tamar–Porapahar Shear Zone) which marks the boundary between two contrasting tectonic blocks of eastern India, namely, the Chhotanagpur Gneissic Terrane (CGC) to the north and Singhbhum Group of rocks to the south. The rocks of the study area are poly-phasedly deformed by three phases of folding, namely, F1, F2 and F3. All the tourmalines are classified to be of ‘Alkali Group’. Chemistry of tourmalines from migmatized quartz tourmaline gneiss and those from quartz tourmaline veins are in conformity with their relation to (earthquake induced) shear system evolution in this terrain. In general, the compositional evolution of tourmaline during prograde metamorphism (∼400°–730°C) has been supported by both petrographic and chemical evidences. Assessment of mineral–chemical data of constituent tourmaline grains clearly suggests compositional variations across zonal boundaries within tourmaline that was controlled by changing metamorphic milieu in this terrane. Field and petrographic evidences clearly indicate activation of earlier and later shears in this region accompanied by infiltration of boron and formation of zoned tourmaline crystals.

Friction Stir Welding Of Magnesium Alloys - A Review

The modern technologies are gaining more and more importance in almost every field and Manufacturing industry not an exception. More and more research has been going on related to welding techniques [1]. Friction stir welding is one of the latest welding techniques that have found a major part in automotive sector. Magnesium alloy one of the major raw material used in these industries due to its light weight, good thermal conductivity, excellent specific strength and stiffness, exceptional dimensional stability, high damping capacity, and high recycle ability [2]. Magnesium alloys can be divided into cast magnesium alloys and wrought magnesium ones in terms of difference in processing [3]. Main commercial magnesium alloys include the AZ series (Mg-Al-Zl), AM series (Mg-Al-Mn), AE series (Mg-Al-RE), EZ series (Mg-RE-Zn), ZK series (Mg-Znmdash;Zr), and WE series (Mg-RE-Zr)[4]. It is thi property which entices automobile manufacturers to replace denser materials, not only steels, cast irons and copper base alloys but even aluminium alloys by magnesium based alloys. Statistically, more than 90% of the magnesium alloy structural components are produced by casting process, especially by various die-casting processes. .Magnesium has a density two-thirds that of aluminium and only slightly higher than of fibre-reinforced plastics and possesses excellent mechanical and physical properties. Compared to using alternative materials, using Mg alloys results in a 22% to 70% weight reduction. Recent developments in coating and alloying of Mg improved the creep and corrosion resistance properties of magnesium alloys for elevated temperatures and corrosive environments. The introduction of this paper gives a detailed review about Friction Stir Welding of Mg alloys. This review work may be a ready reference for subsequent researchers.

Radioelement-bearing Secondary Zoned Apatite around Govardhanagiri-Chinnakolumulapalli-L. Banda Areas of Kurnool District, Andhra Pradesh

Zoned Apatite crystals with intrinsic radioactivity are widespread in the S-type basement granite around Govardhanagiri-Chinnakolumulapalli-L.Banda areas of Kurnool District, A.P. The granite is overlain by Gulcheru quartzite and in turn by Vempalle dolostone of Papaghni Group belonging to the Cuddapah Supergroup. The area (4 km x 6 km) is characterized by conjugate fracture system comprising ENE-WSW and WNW-ESE of varying extents, of which, ENE-WSW is sympathetic to the major deep seated Gani Kalva fault. The apatite crystals are frequently zoned and vary in size from few microns to 1000 microns, occur mostly as veins or associated with pulverized matrix of granite cataclasite. Veins (upto 2 cm. thick) generally follow the major fracture-trend (ENE-WSW) in the area. The apatites are also found intimately associated with fluorite, tourmaline and sulphides, which suggest their derivation from pneumatolytic fluids. The intrinsic accessory uranium as scarce grains of uraninite and other labile phases of granite were remobilized consequent upon the deformation and locked up as ferroan-oxy/hydroxyl inclusions in slowly growing apatite crystals under very low temperature conditions.